Roseanne’s weight was a common topic for the roasters. (Comedy Central)

Roseanne Barr held up her hands in shock, her mouth agape.

Yes, Tom Arnold, her ex-husband, was really on-stage, fidgeting and sweaty as he discussed their failed marriage together.

“Why am I here?” Arnold asked, the answer not readily apparent, but the moment carrying special significance. “I’m here to honor Roseanne and because I earned it. The hard way.”

Roseanne and Tom’s banter – they hadn’t seen each other in 18 years – marked the apex of Comedy Central’s Roast of Roseanne Barr, which aired Sunday night.

Arnold’s appearance was previously publicized, with the comedian a late addition to the roast roster. His speech was emotional and evocative, calling back to Roseanne’s breakthrough appearance on “The Tonight Show” in 1985.

“She got validation from the king that can never be taken away from you,” Arnold said of his ex’s breakthrough. “And, I just want to say, Roseanne, you were my Johnny Carson. Thank you for the thumbs-up, and thank you for allowing me to sit on your couch for a little bit.”

She wore a loud jacket and louder hair on Carson’s show, laughing that innocent laugh of hers and telling jokes about eating, motherhood and suburbia.

Sitcom stardom followed, with “Roseanne” airing from 1988 to 1997, catapulting her to stardom. Roseanne’s TV persona was a working-class hero, the anti-June Cleaver.

Barr’s brashness came with controversy – including her 1990 butchering of “The Star-Spangled Banner” before a San Diego Padres baseball game in which she screeched, grabbed her genitals and spit.

Next came plastic surgeries, a toxic marriage, a talk show and a reality show about life on a macadamia nut farm. These days, Roseanne is a presidential nominee for the Peace and Freedom Party.

The roasters had much material to work with, and Roseanne’s fluctuating weight was a main topic.

“Usually when I roast a pig it has an apple in its mouth,” insult comic Jeffrey Ross said, handing Roseanne an apple (she threw it at him). “Last year we roasted Charlie (Sheen). This year we’re roasting the chocolate factory.”

“Glee” star Jane Lynch served as roast master, with the actress bringing early laughs.

“This show is serving up more old, spoiled hens than Chick-fil-A,” Lynch said. “Oh, that reminds me – f— Chick-fil-A.”

Roasters included Katey Sagal, Wayne Brady, Carrie Fisher and Gilbert Gottfried, who went on a meandering, but hilarious, rant about Rozilla – a hideous monster in Roseanne’s form.

While the event wasn’t live, the roast featured a strong web component, with many of the roasters tweeting during the airing and Comedy Central shairing images and video on a “Roast Dashboard.”

“Wow! Tom Arnold’s set was great!” one Twitter user wrote. “His story at the end was unexpectedly touching!”

The moment was so unconventional for a roast – a chance to consider what used to be, a chance to end a heated feud. Backstage video showed the exes chatting.

“Onward and upward, right?” Roseanne said. “Onward and upward.”

The special closed with Barr singing the National Anthem, a call-back to her ill-advised San Diego screech-fest.

“O’er the land of the free, and the home of the brave,” she sang, raising her arms as the crowd cheered. And it wasn’t awful, and it wasn’t screechy, and it wasn’t insensitive, with Roseanne settling some more old business amid the jokes and barbs.